For all the steamy romance on-screen, the lip-locks oftenleave something to be desired

A lot of straight actors say they like the challenge of ''going gay." It suggests bravery, tolerance, and compassion, and presents the star with an opportunity to deliver his lines with his hands on his hips. So Smith, who was then a rapping TV star, must have seemed extra compassionate in taking this role as a gay con artist and then laying one on the nerdiest member of the Brat Pack. This kiss is terrible because it's not a kiss. Denzel Washington personally advised Smith not to kiss a man in a movie, so in the scene we see Smith put his face near Hall's, and the camera cuts to a reverse angle as he pulls away. There's no proof of contact, but in the scheme of things, this kiss is perfect for a film about a fraud.

Sharon Stone and Sylvester Stallone, ''The Specialist" (1996)

Kissing for the camera must be really hard for these two because they make it seem like an endurance test. Their session begins in a hotel bedroom and proceeds to the bathroom, where both stars flash lots of R-rated flesh. The kissing is PG, however. She doesn't seem to want his face anywhere near hers, pulling back when his mouth opens. Having most of the action take place in a shower is a brilliant diversion strategy. The steam obscures and the water makes it much simpler for the mouths to slide across each other, simulating a kiss.

Oprah Winfrey and Danny Glover,''Beloved" (1998)

Few writers can craft emotionally loaded sex as well as Toni Morrison. This movie completely undoes that. Winfrey and Glover play characters reunited in Ohio after years on the same plantation, and we can feel how drawn he is to her. He caresses the tree of scars on her back, she leads him to her bedroom. The sensuality is palpable. Then Glover's large, hairy face moves in for a trembling kiss that Winfrey, looking as terrified as she does for most of the film, barely catches. A second later, they've cheated by reclining on the bed.

Charlize Theron and Keanu Reeves, ''Sweet November" (2001)

Technically, Reeves's approach to making out with hippy-dippy Theron is sound: He moves to her rhythm; his open mouth initially caresses hers. But it looks like he's hurting her. This is painful to watch. Though apparently this is what the scene requires: He's playing a businessman, and rough kissing signifies control. ''Gentle," she says. And so after a brief recess in a San Francisco downpour, they go at it again. She's overdone the coaching: Now he's too gentle. He goes Gere and timidly presses into her. Yet the two different styles do suggest something significant: Reeves was acting.

Asia Argento and Vin Diesel, ''XXX" (2002)

Triple X? Not with this kiss. It's supposed to be a secret snog in a nightclub between an undercover agent and the moll of the Euro-baddie he's trying to bring down. But the moment is tentative when it needs to be animal. Argento is known to kiss anything like she means it, but Diesel seems intimidated. She leans in and opens her mouth, which causes his lips to tighten and his kissing to soften. Maybe he should have pretended she was a car.

Nobody looks to George Lucas for the libidinal. Still, everything is wrong with this relationship. The hair; the outfits; the dialogue (''Everything here is soft and smooth"); the chemistry. But most wrong of all is a moment George Lucas calls the ''stolen kiss." Anakin Skywalker reaches out to touch the exposed back of Senator Amidala. She turns her head toward his. He gives her a blank stare. She reciprocates, blanker. They kiss, but they might as well each be a blue screen for all the passion they show here.

Kate Bosworth and Kevin Spacey, ''Beyond the Sea" (2004)

How can a connection so apparently wholesome be so unpleasant? This bedtime smooch between Bosworth's Sandra Dee and Spacey's Bobby Darin makes kissing seem like the most uncomfortable thing two people supposedly in love can do. They don't appear to be breathing, and you can practically see thought bubbles over their heads. This is compounded by Spacey's narcissism: He directed, produced, starred, danced, and sang Darin's songs himself, but would it have been too much to let someone else kiss Bosworth?